A wideband, compact monopolar patch antenna with an inherent filtering response is presented in this paper. By employing a slot-assisted mode-tailoring technique, the field distributions of several higher-order modes at the patch center are engineered to produce a stable monopolar radiation pattern with enhanced bandwidth. The closed-form analysis indicates that increasing the current intensity at the central region can transform the conventional TM22mode into one that exhibits a monopolar pattern. This concept is realized by incorporating four slanted slots at the corners of the patch, which constrain the surface current toward the patch center. Besides, these slots also excite an additional slot mode, which serves as a second resonance. At higher frequencies, the slots continue to confine the current distribution of the original TM33mode to a small central region and thereby forming a quasi-TM01monopolar radiation. By combining the three engineered resonances, the proposed single-layer patch achieves a significantly improved bandwidth. (The simulated and measured impedance bandwidths (S11 < -10 dB) are 26.9% and 27.1% respectively). More importantly, the proposed antenna preserves a stable radiation pattern even when the ground-plane size changes. This robustness arises from the slot-assisted mode-tailoring scheme, which strongly confines the current distribution to the central region of the patch. The small-footprint prototype realizes peak gains of 6.92 dBi in simulation and 6.42 dBi in measurement. To ensure the application of the proposed antenna on a vehicle, a large-scale simulation has been performed to verify the wide impedance bandwidth, realized gain and consistent radiation patterns when the antenna is positioned on the roof of a car. While good in-band results are obtained. Radiation nulls are observed near the band edges, resulting from the mutual cancellation of radiated fields. With its broad bandwidth, stable monopolar radiation, and built-in filtering (stopband gain not exceeding 0 dBi), the proposed antenna offers an attractive solution for modern wireless platforms demanding compact form factors and robust interference immunity.

This paper presents a bandwidth-enhanced, low-profile dual-polarization (dual-pol) patch antenna array with a height of only 0.03λ₀ for glass-enclosed mobile platforms in 5G-enabled IoT applications at the millimeter-wave band. The bandwidth improvement and low-profile characteristic are achieved through a single-layer radiating patch fed by closely positioned lateral microstrip resonators, forming a multi-resonance structure that expands bandwidth while reducing the overall height by minimizing vertical feeding components. Dual-pol performance is accomplished via common-mode excitation of back-to-back C-shaped quarter-wavelength resonators on one side of the patch for one polarization, and differential-mode excitation of folded line-shaped resonators symmetrically placed on opposite sides for the orthogonal polarization, achieving extended bandwidth and high isolation. Building on this antenna element, a 1×4 dual-pol phased array is implemented for beam steering, fabricated using high-density interconnect (HDI) technology. Measurements reveal an operating bandwidth of 25.56–28.04 GHz (a fractional bandwidth of 9.5%) forx-pol and 24.42–28.49 GHz (15.6%) for y-pol. Beam scanning across ±45° shows a gain degradation of less than 3 dB, with cross-polarization levels remaining below -20 dB within the main lobe at each scan angle. This design is intended for integration within the camera region of a mobile terminal and has been optimized for operation in an under-glass environment. Performance tests conducted with a glass cover confirm the robustness of the design as an effective under-glass antenna for terminal applications.

In the era of 5G and beyond, the strategic utilization of both sub-6 GHz and millimeter-wave (mmWave) spectrums supports diverse communication services. Through smartphones, consumers can conveniently access a wide range of 5G/6G-enabled Internet of Things (IoT) scenarios anytime and anywhere. In this paper, mmWave and sub-6 GHz aperture-shared antenna and array are proposed for mobile terminals. For the mmWave antenna design, a slot radiating array is integrated into the metallic frame of a smartphone. This design incorporates a differential square-ring feeder and utilizes hybrid mode operation, enabling dual-polarized radiation capability across a wide operating frequency band. Importantly, this configuration requires only two metal layers with a 1.0-mm profile. Sharing the same frame, an inverted-F antenna (IFA) and a hybrid mode antenna with loop antenna and IFA operation are designed to work in sub-6 GHz bands. With the design principle of equal clearance, the sub-6 GHz antennas can perform well with the coexistence of the mmWave array. This approach is particularly applicable for sub-6 GHz antennas of different modes and frequencies. The proposed 1×4 mmWave phased array prototype demonstrates a -10 dB bandwidth of 23.3-30.8 GHz (covering the 5G n257/258 bands), a beam scanning range of ±40∘, and an in-band realized gain above 10.3 dBi. The sub-6 GHz antennas effectively cover 5G bands n1/2/3/7/18/28. By utilizing impedance tuning technique, the lower band can be further tuned to cover the bands n8/5.

In the realm of fifth-generation (5G)-enabled Internet of Things (IoT), the smartphone plays a pivotal role in providing users access to various IoT scenarios. With the emergence of millimeter-wave (mmWave) technology in 5G mobile terminals, it is feasible to realize an ultrabroadband, ultrahigh speed, and ultralow latency communication for advanced IoT applications. However, in a smartphone, the end-fire mmWave radiation is blocked by the metal frame. To solve this problem without altering the industrial design (ID) of the smartphone, we present a new mmWave beam-tilted phased array antenna with multiple hybrid modes operation. Our approach employs a physically oblique radiating aperture to achieve a tilted and frequency-insensitive radiation pattern, effectively addressing the interference from the smartphone platform while preserving the integrity of the ID. To expand the impedance bandwidth, monopole mode, magnetic dipole mode, and stepped patch mode are generated with an effective space utilization. For experimental validation, the proposed prototype is measured in a simplified mobile terminal. The$1\times 4$phased array achieves a −10 dB impedance bandwidth of 23.5–30.5 GHz, which covers the 5G n257 and n258 bands, with an in-band realized gain higher than 9.4 dBi. Furthermore, at 27.0 GHz, a wide 3-dB scanning range of 102.5°/72.0° is obtained for vertical/horizontal polarization, along with a peak gain of 9.4/11.0 dBi. The experimental results validate the proposed beam-tilted antenna solution, indicating that it can effectively address impedance mismatching, radiation distortion, low robustness, and other practical issues in 5G smartphones.

A low-profile dual-broadband dual-circularly-polarized (dual-CP) reflectarray (RA) is proposed and demonstrated, supporting independent beamforming for right-/left-handed CP waves at both K-band and Ka-band. Such functionality is achieved by incorporating multi-layered phase shifting elements individually operating in the K- and Ka-band, which are then interleaved in a shared aperture, resulting in a cell thickness of only about 0.1 λ L . By rotating the designed K- and Ka-band elements around their own geometrical centers, the dual-CP waves in each band can be modulated separately. To reduce the overall profile, planar K-/Ka-band dual-CP feeds with a broad band are designed based on the magnetoelectric dipoles and multi-branch hybrid couplers. The planar feeds achieve bandwidths of about 32% and 26% at K- and Ka-band respectively with reflection magnitudes below −13 dB, an axial ratio smaller than 2 dB, and a gain variation of less than 1 dB. A proof-of-concept dual-band dual-CP RA integrated with the planar feeds is fabricated and characterized which is capable of generating asymmetrically distributed dual-band dual-CP beams. The measured peak gain values of the beams are around 24.3 and 27.3 dBic, with joint gain variation <1 dB and axial ratio <2 dB bandwidths wider than 20.6% and 14.6% at the lower and higher bands, respectively. The demonstrated dual-broadband dual-CP RA with four degrees of freedom of beamforming could be a promising candidate for space and satellite communications.

There has been an increasing interest in addressing the issue of high-resolution inverse synthetic aperture radar (ISAR) imaging from sparse sampling data. Traditional compressed sensing (CS) and matrix completion (MC) methods are based on sparse and low-rank constraints, respectively, which do not make full use of the structure of ISAR data. In this article, a sparse ISAR imaging algorithm using a structured low-rank approach is proposed for enhanced imaging performance. Based on the observation that the structured Hankel matrix has better low-rank property, the proposed algorithm can outperform the group of conventional MC methods in terms of accuracy to data quality and quantity. Rather than using the traditional singular value decomposition (SVD) solution of nuclear norm minimization, the proposed algorithm restates the nuclear norm via an equivalent reformulation that the structured Hankel matrix can be decomposed into two disjointed parts to avoid the dimensional expansion of the Hankel matrix. Meanwhile, the alternative direction method of multipliers (ADMMs) is applied to effectively reduce the computational complexity. Finally, the effectiveness of the proposed algorithm is further validated using the experiments on simulated and measured data.